#include <unordered_map>
class Solution {
public:
    vector<int> FindNumsAppearOnce(vector<int>& nums) {
        unordered_map<int, int> ht;
        vector<int> res;
        for (auto& x: nums) {
            if (ht[x] == 1) {
                ht.erase(x);
            } else {
                ht[x] = 1;
            }
        }
        for (auto& x: ht) {
            res.push_back(x.first);
        }
        sort(res.begin(), res.end());
        return res;
    }
};